What is "cellulitis"

Cellulitis \Cel`lu*li"tis\, n. [NL., fr. L. cellula + -itis.] An inflammantion of the cellular or areolar tissue, esp. of that lying immediately beneath the skin.

1832, from Latin cellula, diminutive of cella "cell" (see cell) + -itis.

n. An inflammation of subcutaneous or connective tissue caused by a bacterial infection

n. an inflammation of body tissue (especially that below the skin) characterized by fever and swelling and redness and pain

Cellulitis is a bacterial infection involving the inner layers of the skin. It specifically affects the dermis and subcutaneous fat. Signs and symptoms include an area of redness which increases in size over a couple of days. The borders of the area of redness are generally not sharp and the skin may be swollen. While the redness often turns white when pressure is applied this is not always the case. The area of infection is usually painful. Lymphatic vessels may occasionally be involved, and the person may have a fever and feel tired.

The legs and face are the most common site involved, though cellulitis can occur on any part of the body. The leg is typically affected following a break in the skin. Other risk factors include obesity, leg swelling, and old age. For face infections a break in the skin beforehand is not usually the case. The bacteria most commonly involved are streptococci and Staphylococcus aureus. In contrast to cellulitis, erysipelas is a bacterial infection involving the more superficial layers of the skin, presents with an area of redness with well-defined edges, and more often is associated with fever. More serious infections such as an underlying bone infection or necrotizing fasciitis should be ruled out.

Diagnosis is usually based on the presenting signs and symptoms with cell culture rarely being possible. Treatment with antibiotics taken by mouth, such as cephalexin, amoxicillin, or cloxacillin, is often used. In those who are seriously allergic to penicillin, erythromycin or clindamycin may be used. When methicillin-resistant S. aureus (MRSA) is a concern, doxycycline or trimethoprim/sulfamethoxazole may, in addition, be recommended. Concern is related to the presence of pus or previous MRSA infections. Steroids may speed recovery in those on antibiotics. Elevating the infected area may be useful as may pain killers.

Around 95% of people are better after seven to ten days of treatment. Potential complications include abscess formation. Bacterial skin infections affected about 155 million people and cellulitis occurred in about 37 million people in 2013. This is about two of every 1000 people per year. Cellulitis in 2013 resulted in about 30,000 deaths worldwide. In the United Kingdom, cellulitis was the reason for 1.6% of admissions to the hospital.